Various field emitters of single crystal diamond

We have fabricated three new differently shaped emitters of single crystal diamond. They are emitter tips shaped like a tall pyramid, a needle, and a candle. The tall pyramidal emitter was grown epitaxially on a fine column with a high aspect ratio. The needle emitter was etched in microwave plasma from a fine column with a high aspect ratio. The candle emitter was etched by the reactive ion etching (RIE) technique using an Al mask shaped like the frustum of a cone. The technology for fabricating new shaped emitters involves forming a fine column on single crystal diamond and reforming the fine column to a sharp tip. The fine column was formed after diamond substrate with an Al dot mask was dry-etched. Although it is usually difficult to obtain both a high aspect ratio (height/diameter) column and a smoothly etched surface, we have fabricated tall fine columns (aspect ratio of 8) on smoothly etched surfaces using a novel RIE technique. It was found that it is important to mix 1similar to2% CF4 gas in O-2 gas. Using a high aspect ratio column, a novel pyramid-shaped tip was fabricated by anisotropic homoepitaxial growth and a needle-shaped tip was fabricated by anisotropic etching in microwave plasma under optimum conditions. After an Al mask shaped like the frustum of a cone was etched with diamond by our novel RIE technique, we were able to successfully fabricate a candle-shaped tip. It was confirmed that the diameter of the emitter tip was less than 80 nm for a tall pyramid-shaped tip, less than 40 nm for a needle-shaped tip and less than 10 nm for a candle-shaped tip.